The present invention relates to a laser measuring system for forming a reference plane by projecting a laser beam in rotary irradiation from a laser rotary irradiation device, for receiving the laser beam by a photodetection device (light receiving device), and for measuring a position of operation or the like.
In the past, a laser rotary irradiation device has been known as a device for forming a reference plane to indicate a reference for operation in a wide range, and a photodetection device has been known as a device for receiving a laser beam and for measuring a position of the reference plane.
A laser rotary irradiation device forms a reference plane by projecting a laser beam with a spot-like luminous flux in rotary irradiation. For instance, by projecting the laser beam in rotary irradiation within a horizontal plane, a horizontal reference plane can be formed. When the laser beam is projected in rotary irradiation within a vertical plane, a vertical reference plane can be formed. When the laser beam is projected in rotary irradiation within a tilted plane, a tilted reference plane can be formed.
A photodetection device has a photodetector for receiving and detecting a laser beam. Based on the laser beam detected by the photodetector, a horizontal reference position, a vertical reference position, etc. can be measured. A laser measuring system can be made up by combining the laser rotary irradiation device and the photodetection device. The laser measuring system using the reference plane formed by the laser beam is used for from the operation in wide range including civil engineering work to the operation in relatively limited space such as room interior finishing work, for example.
In the laser measuring system as described above, the emission light amount of the laser beam of the laser rotary irradiation device is determined for each intended purpose. Usually, the emission light amount of the laser beam is set to a constant value depending on each type of the laser rotary irradiation device. On the other hand, in the case where the distance between the laser rotary irradiation device and the photodetection device is short, the light amount received by the photodetection device is high. In the case where the distance is long, the light amount is low. The photodetection light amount received at the photodetection device varies according to the distance between the laser rotary irradiation device and the photodetection device. The photodetection device has gain control function. Even when there is a change in the light amount of the received laser beam, the gain is adjusted so that the photodetection signal can be within the range of a predetermined level.
In the laser measuring system for performing the surveying operation in wider range, the emission light amount is set to a higher value so that the photodetection device can recognize that the laser beam has been received even when the distance between the laser rotary irradiation device and the photodetection device is long. In this respect, when the photodetection device receives the laser beam at a relatively short distance, the photodetection light amount is too high, and the photodetection light amount is often beyond the adjustment range of the gain control function of a photodetection signal amplifying circuit of the photodetection device. As a result, the photodetection signal reaches saturation.
When the laser measuring system is used in the operation at short distance, the laser measuring system is often so designed that the emission light amount of the laser beam can be manually changed by an operator in order to avoid the saturation of the photodetection signal.
Further, in actual case to use the laser measuring system, the laser rotary irradiation device is in operation at all times when the operation is going on. Moreover, the light amount of the laser beam is set in such manner that the light amount can match the operation at long distance. This means that the laser beam is projected with a higher light amount than it is required in the operation at short distance. This often leads to the waste in power consumption.
To solve the problems as described above, a laser rotary irradiation device has been proposed, in which the position where the photodetection device is installed is kept in memory and the laser beam is emitted only to a space closer to such position (JP-A-11-166832).
However, the laser rotary irradiation device as disclosed in JP-A-11-166832 is not sufficient for energy-saving purpose because the laser light amount is at a constant level. In case there are a plurality of operation points, substantial energy-saving effect cannot be attained.
Further, another type of laser rotary irradiation device has been proposed, in which the reflection light from the object projected by the laser beam is received and the light amount of the laser beam can be adjusted to an adequate value based on the photodetection light amount (JP-A-2006-214850).
However, according to the laser rotary irradiation device disclosed in JP-A-2006-214850, no photodetection device is provided. This means that the system can be applied only in the operation at a relatively short distance, and it is not suitable for the operation in civil engineering work or the like for wider range.